Using ${CDR(disposition)} in extension.conf

how can we use the variable
${CDR(disposition)} = status of the call (ANSWERED, BUSY, NO ANSWER)
if i want to use it in GotoIf(???)
to take some decisive action
what should be the arguments

${CDR(disposition)} ,it is the predefined variable automatically set in cdr_custom.conf in asterisk-1.2 or higher